The present invention relates to serial bus budget development and maintenance. More specifically, the present invention relates to a method for budgeting transactions under a Universal Serial Bus (USB) protocol, utilizing split transactions, such as USB 2.0 (Revision 2.0; Apr. 27, 2000). Present invention is related to application titled, xe2x80x9cMethod and Apparatus for improving Time Constraints and Extending Limited Length Cables in a Multiple-Speed Busxe2x80x9d, filed on Mar. 30, 2001 (Ser. No. 09/823,455) even date herewith.
There are several methods for enabling communication between computers and between a computer and peripheral devices in the art today. One method of communication utilizes the Universal Serial Bus (USB) protocol. USB provides a computer with a means for communicating with up to 127 devices using a single, standardized communication scheme. USB version 1.0 (USB Rev. 1.1; USB Implementers Forum, Inc.) is capable of transmission speeds of 1.5 Megabits (Mbps) (xe2x80x9cLowxe2x80x9d Speed) and 12 Mbps (xe2x80x9cFullxe2x80x9d Speed). A newer version of USB has been developed that incorporates various advantages over USB 1.0, including much accelerated data transmission. Titled xe2x80x9cUSB 2.0xe2x80x9d, the new version is approximately forty times faster than USB 1.0. It transmits data at 480 Mbps, called xe2x80x9chighxe2x80x9d speed (compared to the 12 Mbps of USB 1.0, xe2x80x98fullxe2x80x99 speed).
In order to provide the advantages of USB 2.0, the stringency of many of the timing requirements in the protocol were vastly increased. In addition, various elements were added to provide for speed translation, etc., adding to the protocol""s complexity.
A method for USB 1.0 budget development is known in the art. Although the USB 2.0 specification describes potential for budgeting/scheduling transactions, it does not provide any particular method for achieving this. As described below, means used according to USB 1.0 would be ineffective for budgeting USB 2.0 transactions. In addition to other problems, a method for budgeting USB 2.0 transactions must accommodate for transaction translation between high speed and fall/low speedxe2x80x94a capability that USB 1.0 budgeting means do not possess.
Accordingly, there is a need for an improved method and apparatus for budgeting transactions under a USB protocol.